Field of the Invention
Embodiments of the present invention relate generally to a blanking device for multi charged particle beams, and a multi charged particle beam writing apparatus, and more specifically, to a blanking device mounted in a multi-beam writing apparatus, for example.
Description of Related Art
The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. The electron beam writing technique, which intrinsically has excellent resolution, is used for writing or “drawing” a mask pattern on a mask blank with electron beams.
As an example employing the electron beam writing technique, a writing apparatus using multiple beams (multi-beams) can be cited. Compared with the case of writing a pattern by using a single electron beam, since it is possible to emit multiple beams at a time in multi-beam writing, the throughput can be greatly increased. For example, in a writing apparatus employing a multi-beam system, multi-beams are formed by letting portions of an electron beam emitted from an electron gun pass through a corresponding hole of a plurality of holes in the mask, each of the beams is blanking-controlled, and each unblocked beam is diminished by an optical system to reduce a mask image and deflected by a deflector so as to irradiate a desired position on a target object or “sample”.
In the multi-beam writing, when performing highly precise writing, the dose of an individual beam is individually controlled by an irradiation time in order to give a specified dose onto each position on a target object. For highly accurately controlling the dose of each beam, it is necessary to carry out blanking control at high speed to perform a beam ON/OFF control. Conventionally, in a writing apparatus of a multi-beam system, a blanking control circuit for each beam is placed on a blanking plate where each blanking electrode of multi-beams is arranged. Controlling is independently performed for each beam. For example, a trigger signal for causing a beam to be ON is sent to control circuits of all the beams. In responsive to the trigger signal, the control, circuit of each beam applies a beam-ON voltage to an electrode, and simultaneously, starts counting the irradiation time period by a counter. Then, when the irradiation time has been completed, a beam-OFF voltage is applied. In performing such a control, a ten-bit control signal has been used, for example. However, since the space for placing a circuit on a blanking plate and the amount of current to be used are restricted, there is no other alternative but to have an uncomplicated circuit for the amount of information of control signals. Therefore, it has been difficult to build in a blanking circuit that can perform an operation of high speed and high precision. Further, installing a blanking control circuit for each beam on a blanking plate restricts narrowing the pitch of multi-beams. By contrast, when placing a control circuit for each beam outside the blanking plate and connecting them by wiring in order to secure a space for installing the circuit, since the wiring becomes long, there is a problem that crosstalk increases and writing precision degrades.
In order to solve the above problem, there is proposed a mechanism where, in addition to individual blanking electrodes for respective beams, deflectors are provided outside the ends of the multi-beams, in the latter part of the optical path, in a manner such that the deflectors sandwich the entire multi-beams so as to control the exposure time by collectively deflecting the entire multi-beams at high speed by the deflectors (e.g., refer to Japanese Patent Application Laid-open (JP-A) No. 2014-112639).